Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
  • H04L25/40—Transmitting circuits; Receiving circuits
  • H04L25/49—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems
  • H04L25/4906—Transmitting circuits; Receiving circuits using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems using binary codes

Definitions

• the invention relates to a method for recovering data transmitted via a transmission link for digital data streams from the transmitting end to the receiving end at the receiving end.
• Codeword generator generated binary codeword, which gives a Dirac pulse in an auto-correlated manner, and are coded by means of the codeword generator by cyclically shifting its further binary codewords generated by one codeword and the inverse codewords obtained therefrom by inverting and
• a cross-correlation of the code word received is carried out by evaluating the relative position and the sign of the main maximum of the respective cross-correlation function for recovering the data.
• telcom report 14 (1991), number 2, pages 104 to 107
• a 2 m sequence is used as the binary code word, which ideally results in a Dirac pulse in an autocorrelated manner.
• further binary code words are generated by cyclical shifting, each of which is distinguished from one another by different phases.
• 31 different data words can be encoded on the transmission side and thus 4-bit data words encoded; 5-bit data words cannot be coded because only 31 code words are available.
• One in terms of the number of encodable Data words of an improved embodiment of the known method consists in that inverted binary 2 m sequences are used on the transmitting side in addition to the coding.
• 5-bit data words can thus be transmitted and can be recovered on the receiving side by means of cross-correlation despite interference on the transmission path, provided that no more than 7-bit errors occur during transmission.
• the invention is based on the object of designing the method described at the outset in such a way that a comparatively high number of data present on the transmission side can be reliably recovered on the reception side.
• another code word set is used, the one of which a code word generated by a further code word generator auto-correlates a Dirac pulse, the other binary code words of which are generated by cyclically shifting its one code word and its inverse code words by inverting, - the further code word generator being generated by on
• a number of data are encoded with data polynomials of the seventh degree by assigning the data polynomials formed therefrom with the five lowest binary digits of the data polynomial of the seventh degree to the code words of the two code word generators as a function of two value combinations of the two highest binary digits of the data polynomial of the seventh degree, -
• a further number of data are encoded with data polynomials of the seventh degree by the data polynomials formed therefrom with the five lowest binary digits of the data polynomial of the seventh degree, the inverse code words of the two code word generators in
• an additional number of data are encoded with data polynomials of the seventh degree, in that data polynomials formed therefrom, each with zero at the five lowest binary positions of the data polynomial of the seventh degree, are assigned code words of an additional code word set depending on four value combinations of the two highest binary positions of the data polynomial of the seventh degree,
• the additional code word set is generated by means of an additional code word generator that matches the two other code word generators with regard to the degree of its generator polynomial and its code words,
• a major advantage of the method according to the invention is that it has more than twice as many Code words are made available on the transmission side as in the known method. However, it must be accepted that the number of bit errors must not exceed the value 5 if, on the receiving side, cross-correlation is to ensure the reliable recovery of the data given on the transmission side on the transmission link.
• the code words of the additional code set can be formed in different ways. For example, it is possible to use four different code words generated by cyclically shifting the one binary code word of the additional code word generator. However, it is considered to be particularly advantageous if two code words from the additional code set are used and the further code words are formed therefrom by inverting.
• FIG. 1 shows an embodiment of a shift register suitable for generating a code word for the method according to the invention, in FIG. 2 representation of a binary code word, in
• FIG. 4 an embodiment of a bipolar encoder
• FIG. 5 shows a table to illustrate the coding or decoding
• FIG. 6 shows an exemplary embodiment of an arrangement for carrying out the method according to the invention
• FIG. 7 shows the course of a cross-correlation function
• FIG. 8 shows the courses of three cross-correlation functions.
• FIG. 1 shows a shift register 1 which contains five stages 2, 3, 4, 5 and 6, each of which is formed by a D flip-flop in the exemplary embodiment shown.
• the shift register 1 is fed back in the manner shown in FIG. 1, an exclusive OR element 7 being arranged between the stages 3 and 4; another exclusive OR gate 8 is upstream of stage 2.
• This feedback can be described by a generator polynomial G KK (r (x):
• An input sequence E (x) can be applied to the shift register 1 at an input 9; A binary output sequence A (x) can be removed at an output 10.
• the output signal A (x) is through with the input signal E (x) and the generator polynomial G KKF (x)
• Output signal which is only one period of the 2m sequence represents and is thus the polynomial representation of c ⁇ Cn).
• Output signal of the shift register can be found in the table in FIG. 2, which has been drawn up taking into account the fact that the contents of the individual stages 2 to 6 of the shift register according to FIG. 1 can be described by the polynomial I (x):
• code words have a length of 31 and enable 31 different phase positions s of the 2 m sequence, so that 31 different code words are available in this way are.
• cyclic codes have an irreducible generator polynomial G (x) with degree g as a characteristic.
• Codewords C (x) in general are now generated in such a way that the so-called cyclic addition R (x) is appended to a data word D (x), so that the codeword polynomial C (x) can be divided by G (x) without any residuals. To do this, first multiply D (x) by x 9 and then R (x) by dividing
• R (x). D (x) jmod G (x) (12) receives.
• the cyclic addition can now be obtained by using a data value for E (x) in Eq. (12) and dividing it by G (x).
• the result can then be separated into the result coefficient E (x) and the remaining remainder R (x).
• Essential for the code word calculation is only the result for R (x) in the
• the stock of a total of 31 code words can be doubled by inverting to obtain 31 inverse code words, if one.
• bipolar encoder is used, as shown in Figure 4.
• the code word generator shown here has a feedback shift register 20 with the generator polynomial G, (x) with a plurality of stages 21 to 24 (a total of 26 stages) and exclusive-OR gates 25 and 26.
• a further exclusive OR gate 27 is arranged downstream of the shift register 20 in that it is connected directly to the output of the exclusive OR gate 26 with an input 28 and can be connected to the output of stage 24 via a changeover contact 29 in its position a . In position b of the changeover contact 29, one input 28 is acted upon by the signals from the lower five digits d to de of a data word D (x).
• the further input 30 of the further exclusive OR gate 27 is acted upon by the signal of the uppermost (sixth) position of the data word D (x).
• the sixth position controls the inversion, so that here 62 different code words are available, if we continue to assume a 2 m sequence as an example.
• the sixty-two different code words forming a first code word pool are thus one-half of that by means of a code word generator
• the code set C '(x) generated with the bipolar encoder according to FIG. 4 is described in the table shown by specifying the generator polynomial G, (x) with reference to the inversion, in FIG. 5 with “b” any states are marked with "0" or "1".
• the further code word supply is identified in the table by specifying the generator polynomial G 2 (x), while G, (x) indicates code words of the additional code word supply with the additions a to d.
• data words D (x) can be transmitted in this way Encode test data that represent 7-bit words with the binary digits d-, - ⁇ j .
• the procedure is such that an abbreviated data word D. (x) of the fifth degree is obtained from the data words D (x) of the seventh degree, which has the five lowest digits of the data word D (x) of the seventh degree.
• This shortened data word D k () of the fifth degree depending on the combination of values at the positions d g and d-, the data word D (x) of the seventh degree, has inverted or non-inverted code words of the one code word supply and the further code word supply assigned.
• the code words formed by means of the code word generators described above with the generator polynomials G, (x), G 2 (x) and G, (x) are stored in a coding device 40, which is an addressable memory can act.
• the code words generated according to the generator polynomial G -, (x) are located at memory locations 41, their inverse code words at memory locations 42 and the code words generated according to the generator polynomial G 2 (x) are located at memory locations 43, their inverse code words at memory locations 44 and the additional code words at storage locations 45 or their inverse code words at storage locations 46.
• Shown in block 47 and closed Coding data words are coded in the coding device 40 in a manner as described above and transmitted as coded data (block 48) via a transmission link 49, where they are encoded as data that is more or less corrupted by the transmission link 49 (block 50 ) are pending and three cross-correlators 51, 52 and 53 are fed.
• the cross correlators 51 to 53 have different 2 - sequences as correlation references:
• correlation references are generated with the generator polynomials G, (x), G 2 (x) and G -, (x).
• the cross correlator 51 thus has the correlation reference M, (x)
• the cross correlator 52 has the correlation reference M 2 (x)
• the cross correlator 53 has the correlation reference M 3 (x).
• the code words generated with a specific generator polynomial generate an evaluable maximum with the value 31 in only one of the three cross-correlators. Only smaller maxima arise in the other two cross-correlators, as can be seen in FIG. 8 z.
• the uniqueness of the maximum applies in the course of kKKF, (n) also for falsified code words.
• the value of the main maximum in KKF, (n) decreases by the value 2 and at the same time the maximum values of the secondary maxima in KKF 2 (n) and KKF 3 (n) increase by a maximum of 2 per bit error in the code word.
• the detection threshold for a maximum in the course of the function of the cross-correlation In order to obtain a maximum error tolerance in the correlative decoding, the detection threshold for a maximum in the course of the function of the cross-correlation
• the data word D (x) can be determined directly by means of a downstream memory (not shown) using the table according to FIG Main maximums in the cross correlator 51 with the correlation reference M -, (x) determines that C (x) was generated with G, (x).
• the positions d ⁇ to d- of the data word D (x) are thus determined to be 0 according to FIG.
• the location of the main maximum now determines the value of d.
• the method according to the invention can also be used the number of bit errors while evaluating the amount of
• Main maximums are determined in a corresponding manner.
• the method according to the invention is also not restricted to the use of code words of a certain length, a certain number of cross-correlators and a certain number of generator polynomials; however, the number of cross-correlators must match the generator polynomials.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Error Detection And Correction (AREA)
• Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
• Mobile Radio Communication Systems (AREA)

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• 1992
  • 1992-01-31 DE DE4203301A patent/DE4203301C1/de not_active Expired - Fee Related
• 1993
  • 1993-01-26 US US08/284,402 patent/US5504781A/en not_active Expired - Fee Related
  • 1993-01-26 WO PCT/DE1993/000082 patent/WO1993015574A1/de active IP Right Grant
  • 1993-01-26 EP EP93902071A patent/EP0624294B1/de not_active Expired - Lifetime
  • 1993-01-26 AU AU33443/93A patent/AU3344393A/en not_active Abandoned
  • 1993-01-26 AT AT93902071T patent/ATE130143T1/de not_active IP Right Cessation
• 1994
  • 1994-07-26 NO NO942785A patent/NO942785L/no unknown

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